Z-source inverter control for traction drive of fuel cell - battery hybrid vehicles

This paper presents a Z-source inverter control strategy used to control power from the fuel cell, power to the motor, and state of charge (SOC) of the battery. The Z-source inverter utilizes an exclusive Z-source (LC) network to link the main inverter circuit to the fuel cell (or any dc power source). A new concept is revealed that substitutes a high voltage battery for one (or both) of the capacitors from the Z-source network. By controlling the shoot-through duty cycle we can control the battery voltage (thus controlling SOC) therefore there is no need for a separate dc-dc converter. By controlling the shoot-through duty cycle and modulation index we can produce any desired output ac voltage, thus there is no need for a dc-dc boost converter. These facts make the Z-source inverter highly desirable for use in hybrid electric vehicles, as the cost and complexity is greatly reduced when compared to traditional inverters. These new concepts are demonstrated by simulation and experimental results.